1. Field of the invention.
This invention relates to relief valves and more particularly to a combination double acting valve responsive to vacuum and/or pressure to prevent explosion or implosion of a fluid containing Vessel.
2. Description of the prior art.
Industrial relief valves are currently used for the release of excess pressure to prevent damage to a vessel or tubular line, the environment or personnel. There is a need for a combination pressure and vacuum relief valve for use on a vessel containing fluid such as carbon dioxide where excessive pressure must be released to prevent explosive damage to the vessel or in the event a drain valve is opened and a vacuum is generated within the vessel to prevent an implosion thereof.
The most pertinent patent is believed to be U.S. Pat. No. 4,977,918, issued Dec. 18, 1990, to Taylor for Pressure/Vacuum Relief Valve. This patent discloses a piston divided cylinder communicating with a vessel at one end, on one side of the piston, and communicating with the atmosphere at its other end on the other side of the piston. The piston has a rod extending through both ends of the cylinder and a cage surrounding a fuse-like pin at respective ends of the cylinder and piston rod which is ruptured in response to excessive pressure in one end of the cylinder or a vacuum in the opposite end of the cylinder to release the pressure or admit atmospheric air to the vessel. The pressure/vacuum relief valve of this patent functions quite well, however, it is bulky in structure and the complexity of its components is not conducive to economy.
This invention provides a compact structurally simplified vacuum/pressure relief valve which releases excess pressure or admits ambient air to a vessel having lower than atmospheric pressure.